In the field of automotive diagnostics, most automotive vehicles currently employ a distribution of electro-mechanical sensors for providing electronic inputs to an Electronic Control Unit (ECU), which typically includes a microprocessor and memory for processing embedded algorithms. For example, the Engine Control Module (ECM) performs such functions relating to proper operation of an engine and drive train of an automotive vehicle. A primary function of the ECM is the reduction of undesirable engine emissions, however ancillary tasks, such as environmental control, comfort controls, safety systems, etc, are also currently performed by additional ECUs.
Each sensor in a sensor suite typically measures a single desired metric that is associated with one of a plurality of various aspects of automotive vehicle operation. Examples of such metrics include, but are not limited to, temperature, airflow, fuel flow, throttle position, vehicle speed, vehicle transmission gearing, and exhaust emission characteristics. Each sensor in turn emits an electronic signal that is proportional to the individual metric being monitored.
While monitoring the plurality of electrical outputs from the plurality of sensors, the microprocessor calculates a plurality of output parameters that are applied to a plurality of servomechanisms. For example, the ECM performs this function for metering desired amounts of fuel and air, and for setting ignition timing. Transmission gearing ratios are controlled by a Transmission Control Module (TCM) in an ECM/TCM configuration or a Powertrain Control Module (PCM) as specified in SAE J1930.
During ordinary operation, the sensors transmit electrical signals that are within predetermined limits. This allows the Electronic Control Unit (ECU) to make necessary corrections to related parameters so as to restore sensor outputs to predetermined levels. When any one of the sensors transmits an electrical signal having a level that is not within predetermined limits, a fault is detected and an error signal generated, which error signal identifies the sensor that generated the fault condition as well as the nature of the fault. Considered collectively, the error signals are known as Diagnostic Trouble Codes (DTCs). Current automotive vehicles provide a standardized data transfer port to allow the microcomputer to export the DTCs to an external monitoring device for display to a servicing mechanic. By tracing a table of these DTCs, the mechanics ability to troubleshoot and correct a problem associated with current operation of the vehicle is enhanced.
In current vehicles, on-going data are provided to the Electronic Control Unit (ECU) and thus to the external monitoring device. In addition, some ECUs will store a Freeze Frame (regulatory requirement) or Failure Record. Thus, while current operating parameters may be readily available to identify current problems, intermittent problems are not readily isolated and repaired if the fault is not present during diagnostic monitoring by the mechanic. More specifically, there is currently no provision for storing relational sensor data both before and after a fault condition occurs nor is there a provision for storing relational sensor data from networked ECUs that are not currently detecting a DTC. Examples of such non-diagnosable faults are significant hesitations that may occur during acceleration from particular vehicle speeds or while the transmissions are at higher gear ratios. There is a need for systems and methods that address such issues with current ECUs.